AWS

The AWS integrations live in a separate repository and ship as their own packages, so an application that never touches AWS does not carry the SDK.

Source: github.com/ipjohnson/Hardened.Amz

Lambda runtimes for functions, API Gateway, DynamoDB Streams and SQS; a DynamoDB client library; CDK constructs; and the test harnesses for all of them.

What is here

Area	Page	Repository path
Plain Lambda functions	Lambda functions	src/Lambda/Function
HTTP behind API Gateway	API Gateway	src/Lambda/Web
DynamoDB stream records	DynamoDB Streams	src/Lambda/DynamoDbStream
SQS batches	SQS	src/Lambda/Sqs
DynamoDB clients	DynamoDB client	src/Clients/DynamoDb
Infrastructure	CDK	src/Hardened.Amz.Cdk
Test harnesses	Testing AWS handlers	—

The shape of it

A Lambda application is a module like any other, and the runtime module it imports is the only thing that changes. A handler, its filters, its parameter binding and its configuration do not know they are on Lambda.

using Hardened.Amz.Function.Lambda.Runtime.DependencyInjection;
using Hardened.Requests.Abstract.Attributes;
using Hardened.Shared.Runtime.Attributes;

[HardenedModule]
[LambdaFunctionModule]
public partial class Application { }

public class OrderHandler {
    [HardenedFunction("process-order")]
    public OrderResponse ProcessOrder(OrderRequest request) {
        return new OrderResponse { OrderId = Guid.NewGuid().ToString() };
    }
}

The same handler behind API Gateway is a route rather than a function name:

[HardenedModule]
[LambdaWebModule]
public partial class Application { }

public class ProductController {
    [Get("/api/products/{id}")]
    public Product GetProduct(string id) => _repository.Find(id);
}

What the runtime gives you

Structured CloudWatch logging. Each runtime replaces ILoggerProvider with one that writes structured lines CloudWatch Logs Insights can query, with the request id attached.

Embedded metrics. IMetricLogger writes the CloudWatch Embedded Metric Format, so metrics come out of the log stream without an extra API call.

Partial batch responses. The SQS and DynamoDB Stream runtimes fork the execution chain per record and report exactly which records failed, so a batch of ten with one bad message redelivers one message rather than ten.

The log level from the environment. Information, or Debug in development and test, overridden by LOG_LEVEL. See Environments.

Cold start

Routing tables, service registrations and parameter binding are all emitted during the build, so a cold start does no assembly scanning and no reflection over your types. On its first invocation the process constructs a service provider from a list of registrations and calls a method.

The runtimes are compatible with trimming and Native AOT: every registration is a literal typeof() the trimmer can follow.

The core repository

• Hardened.Framework — modules, dependency injection, routing, binding and testing, covered in the Guide